1. Field
Example embodiments relate to a memory device and/or methods of manufacturing and operating the same, and more particularly, to a magnetic random access memory (MRAM) having an increased On/Off ratio and/or methods of manufacturing and operating the MRAM.
2. Description of the Related Art
A magnetic random access memory (MRAM) is a random access memory (RAM) that reads data written on a magnetic tunnel junction (MTJ) by measuring a resistance difference from magnetization states of a free layer and a pinned layer. A magnetization direction of the pinned layer is fixed. A magnetization direction of the free layer may change when a magnetic field having a set (or, predetermined) intensity is applied to the free layer. Also, a magnetization direction of the free layer may change depending on a spin state of an electric current flowing through the MTJ. A resistance measured when magnetization directions of the free layer and the pinned layer are the same is called an “on” resistance, and a resistance measured when magnetization directions of the free layer and the pinned layer are the opposite is called an “off” resistance. The MRAM may read data by using a difference between the “on” and “off” resistances. Therefore, when the difference between the “on” and “off” resistances in the MRAM is little, in other words, when an on/off ratio is small, a sensing margin decreases, thereby making read-data less reliable. Problems such as overlapping of cell distribution and array size reduction may occur as well. Especially, when the resistance increases as a degree of integration increases, the sensing margin may decrease more.